Combustor construction with means for prevention of hot streaks



Aug. 21, 1962 A. H. LABASTIE ETAL 3,049,882 COMBUSTOR CONSTRUCTION WITHMEANS FOR PREVENTION OF HOT STREAKS Filed May 16, 1960 INVENTORJ. 418587A. Ana/7:775 fan/0v Wt-JZEE pan/4Z0 6 524114665 United States Patent3,049,882 COMBUSTOR CUNSTRUCTION WITH MEANS FDR PREVENTION OF HOTSTREAKS Albert Henry Labastie, Marblehead, and Edwin Wester, Lynnfield,Mass, and Donald Charles Blowers, Broad Albin, N.Y., assignors toGeneral Electric Company, a corporation of New York Filed May 16, 1960,Ser. No. 29,358 4 Claims. (Cl. ell-39.66)

This invention relates to combustor constructions, and particularly toan improved combustor construction having means for prevention of hotstreaks therein.

In a conventional gas turbine engine, an axial flow air compressordelivers compressed air through a diffusing section to a fuel combustor.The flow path for the compressed air is formed between concentricspaced-apart stationary casing members, and it is convenient to supportan inner one of the casing members by means of a plurality ofcircumferentially-spaced radially extending struts, which are secured attheir extremities to the casings. However, in the interest of minimizingthe axial length of the engine, the diffuser section is given as shortan axial length as is feasible for performance of its function, with theresult that the struts must be located in close proximity to the leadingedge of the combustor. We have found in practice that such location ofthe supporting struts causes the wakes which form downstream of thestruts to establish an uneven distribution of air flow over the leadingsurfaces of the combustor, thus producing hot streaks in the combustordirectly downstream of the struts, where there is an inadequate flow ofair for cooling purposes.

It is the object of this invention to provide a combustor constructionwith improved means for reducing wake formation by supporting strutslocated upstream of the combustor, to prevent the development of hotstreaks on the leading surfaces of the combustor.

This and other objects and advantages of our invention will becomeapparent from the following detailed description.

Briefly stated, in accordance with one aspect thereof, we carry out ourinvention by forming indentations or saddles in the leading surfaces ofa combustor to cause the scooping of a substantial flow of air into thesaddles, and by locating the trailing edges of struts located upstreamof the combustor in spaced-apart proximity to the saddles. The flow ofair scooped by the saddles sweeps the area behind the struts, andreduces the effect of turbulent wake-formation downstream of the struts.The loss of axial velocity associated with wake-formation is thusreduced, with the result that an increased flow of cooling air occursover the leading surfaces of the combustor downstream of the struts.

The air scooped into the saddle is forced to flow ally outwardly andinwardly therefrom by means of a battle portion formed at the axiallydownstream end of the saddle, thus cooling the leading surfaces of thecombustor downstream of the strut. This construction forces suflicientcooling air to flow into the saddle to effectively prevent the formationof hot streaks on the leading surfaces of the combustor.

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which we regard as ourinvention, it is believed that the invention will be better understoodfrom the following description taken in connection with the accompanyingdrawing, in which:

FIG. 1 is an elevation in section of a portion of a gas turbine enginemade according to our invention;

FIG. 2 is a pictorial view of a cutaway portion of the strut andcombustor of FIG. 1; and

radi- Patented Aug. '21, l$62 FIG. 3 is a view taken along line 3-3 inFIG. 1, looking in the direction of the arrows.

Referring to the drawing, an illustrative embodiment of our invention isshown in a strut 1, having a trailing edge 1a, and a combustor 2. Thecombustor may be cylindrical or toroidal in form, to provide aconventional cannular or annular combustion system, respectively. Forpurposes of illustration, combustor 2 is shown as an annular system,comprising circurnferentially spaced apart inner and outer annular walls3 and 4, respectively. These elements are incorporated in a gas turbineengine generally designated 6, in which an annular air flow path 7 isformed between an outer annular casing 8 and an inner annular casing 9which are circumferentially spaced apart. In a conventional manner, acompressor (not shown) supplies compressed air to a diffuser portion 10formed between casings 8 and 9, exhausting thereto through a pluralityof circumferentially spaced flow-straightening vanes 11 which extendacross the passage 7. Subsequent to diffusion of the compressed air, itis delivered to combustor 2, flowing in the directions generallydesignated by the arrows. In a well known manner, fuel is injected intothe interior of combustor 5 by means of a nozzle 12 from fuel supplymeans 13 located exteriorly of casing 8. Compressed air received fromdiffuser 10 is caused to flow into the interior of combustor 2 throughsuitable openings (not shown) in order to effect combustion of the fuelinjected therein.

Combustor 2 includes a dome 14 partially enclosing the combustion space,and a cowl portion 15 extending upstream for even division of the airflow into inner and outer portions of the air passage, designated 7a and7b respectively. Cowl 15 terminates in a nose 16, and partiallycomprises the leading surfaces of combustor 2. Subsequent to combustionin combustor 2, the hot gases are exhausted to a turbine (not shown) anddischarged to provide a useful thrust reaction, in a manner well knownin the art. No further description of the engine construction, which initself forms no part of the present invention, is believed necessary.

In carrying out our invention, we form cowl 15 with an indentation orsaddle 17 for each strut 1, and locate the trailing edge in of the vanein axially-spaced proximity to this indentation. In the preferredembodiment shown, the trailing edge of the vane 1 is axially inset intothe saddle 17. As shown, saddle 17 is formed with a pair ofcircumferentially spaced apart walls 18 and H extending with a componentof direction generally radial to passage 7 and converging in adownstream direction, and terminates in a bafiie portion 20 extendinggenerally transversely to the direction of flow. We prefer to formbaffle 20 with a V-shaped cross-section forming an apex 21 extending ina direction lying in the plane of FIG. 3, so as to obtain division ofthe air stream in saddle 17 into air passages 7a and 7b, with a minimumdisturbance of flow. Walls 18 and 19 are spaced circumferentially of thecombustor from strut 1 to provide for the collection in the saddle of asubstantial flow of air,

The position of the strut,'inset into the saddle, causes the area behindthe strut to (be swept by air scooped into the saddle, reducing theeffect of turbulent wake-formation and consequent loss of axial velocityof the air, and thus produces an increased flow of cooling air for thecombustor surfaces directly downstream from the strut. This constructionis effective to prevent the formation of hot streaks in the combustorsurfaces due to wake formation behind the strut. The relative dimensionsand locato maintain an adequate cooling air flow over the trailing edgesof the strut and over the surfaces of baffle and walls 3 and 4.

It is not necessary to the invention that the trailing edge 1a of thestrut be axially inset into the saddle as in the preferred embodimentshown; the trailing edge 1a may be spaced axially upstream of the nose16, provided that it is located with sufficient proximity to the saddleto render the flow of air scooped by the saddle operative to reduce theformation of a turbulent wake and the resulting loss of axial velocitydownstream of the strut. In any event we have discovered that to reduceturbulent wake formation, the peripheral spacing of the strut 1 from thewalls 18 and 19 of the cowl 15 must be in excess of one and one halfpercent (l /2%) of the strut width. Spacing greater than two and onehalf percent (2 /2 of the strut width, however, provides littleadditional improvement.

It will be apparent from the foregoing description that we have providedan improved combustor construction with means for preventing theformation of hot streaks therein, which would otherwise be induced bythe presence of a strut immediately upstream of the combustor. While wehave shown and described a particular embodiment of our invention, itwill be apparent to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe invention. We intend in the appended claims to cover all suchchanges and modifications.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A combustor construction for a gas turbine engine comprising, incombination; an inner casing and an outer casing circumferentiallyspaced apart to form an annular fluid passage therebetween, at least onevane extending radially across said passage, a combustor mounted in saidair passage and extending downstream from said vane with respect to thedirection of fluid flow in said passage, an upstream end of saidcombustor formed with an indentation, said vane located in axially andcircumferentially spaced apart proximity to said indentation by anamount not less than one and one half percent (l /2%) or substantiallygreater than two and one half percent (2 /2%) of the width of said vane,such that a flow of fluid is scooped into said indentation from saidpassage to flow downstream of said vane through said indentation tooppose the formation of a turbulent wake downstream of said vane therebyinhibiting the formation of hot streaks along said combustor.

2. A combustor construction for a gas turbine engine comprising, incombination; an inner casing and an outer casing circumferentiallyspaced apart to form an annular fluid passage therebetween, at least onevane formed with a trailing edge and extending radially across saidpassage, a combustor mounted in said air passage'and extendingdownstream from said vane with respect to the direction of fluid flow insaid passage, an upstream end of said combustor formed with anindentation, said trailing edge of said Wane located incircumferentially and axially spaced apart proximity to said indentationby an amount of not less than one and one half percent (l /2%) orsubstantially greater than two and one half percent (2 /2%) of the widthof said vane, such that a flow of fluid is scooped into said indentationfrom said passage to flow around and downstream of said trailing edge ofsaid vane through said indentation to oppose the formation of aturbulent wake downstream of said vane thereby inhibiting the formationof hot streaks along said combuster.

3. A combustor construction for a gas turbine engine comprising, incombination; an inner casing and an outer casing circumferentiallyspaced apart to form an annular fluid passage therebetween, at least onevane formed with a trailing edge and extending radially across saidpassage, a combustor mounted in said air passage and extendingdownstream from said vane with respect to the direction of fluid flow insaid passage, an upstream end of said combustor formed with anindentation, said trailing edge of said vane axially inset into saidindentation in circumferentially and axially spaced apart relationthereto by an amount not less than one and one half percent (l /2%) norsubstantially greater than two and one half percent (2 /2 of the widthof said vane, such that a flow of fluid is scooped into said indentationfrom said passage to flow around and downstream of said trailing edge ofsaid vane through said indentation to oppose the formation of aturbulent wake downstream of said vane thereby inhibiting the formationof hot streaks along said cornbustor.

4. A combustor construction for a gas turbine engine comprising, incombination; an inner casing and an outer casing circumferentiallyspaced apart to form an annular fluid passage therebetween, at least onevane extending radially across said passage, an annular combustormounted in said air passage and extending downstream from said vane withrespect to the direction of fluid flow in said passage, said combustorformed with a nose at the upstream end thereof, said nose formed with anindentation, said indentation comprising a pair of spaced apart wallsextending with a component of direction generally radial to saidpassage, said indentation further comprising a baffle portion extendingtransversely to the general direction of fluid flow through said passageand joining said walls. at the downstream ends thereof, said vanelocated in spaced apart relation to said walls and in axially spacedapart relation to said .baflle portion by an amount not less than oneand one half percent (l /2%) nor substantially greater than two and onehalf percent (2 /2 of the width of said vane, such that a flow of fluidis scooped into said indentation from said passage to flow around anddown stream of said vane to oppose the formation of a turbulent wakedownstream of said vane thereby inhibiting the formation of hot streaksalong said combustor.

References Cited in the file of this patent UNITED STATES PATENTS

